Shaopeng Wei

Isolation, biological evaluation and 3D-QSAR studies of insecticidal/narcotic sesquiterpene polyol esters

AbstractFor the first time, a set of (43) natural sesquiterpene polyol esters isolated from the root bark of Celastrus angulatus Maxim and Euonymus japonicus Thunb were subjected to 3D-QSAR comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) studies, with the aim of proposing novel sesquiterpene-based compounds with optimal narcotic or insecticidal activities. The established 3D-QSAR models exhibit reasonable statistical quality and prediction capabilities, with internal cross-validated Q2 values of ∼0.5 and external predicted R2 values of >0.9, respectively. The relative contributions of the steric/electrostatic fields of the 3D-QSAR models show that the electronic effect governs the narcotic activities of the molecules, but the hybrid effect of the electrostatic and hydrophobic interactions is more influential in the insecticidal activities of the compounds. These findings may have valuable implications for the development of novel natural insecticides. FigureA 3D-QSAR study using CoMFA and CoMSIA methods was carried out on a series of 43 natural insecticidal/narcotic sesquiterpene polyol esters. The CoMSIA models showed excellent predictive capabilities.

Two New Members of Streptothricin Class Antibiotics from Streptomyces qinlingensis sp. nov

Four streptothricin-group antibiotics (1~4) were isolated from the fermentation broth of Streptomyces qinlingensis sp. nov. Along with the known antibiotics streptothricins F (1) and D (3), two new members of this class (2, 4) were identified as 12-carbamoyl derivatives of 1 and 3, respectively, mainly by analysis of the IR, HR-MS and NMR spectral data. The antibacterial activities of 1~4 against Escherichia coli (MICs 3.1, 25.0, 3.1 and 12.5 μg/ml), Bacillus subtilis (MICs 6.3, 25.0, 3.1 and 50 μg/ml), Staphylococcus aureus (MICs 12.5, >100.0, 6.3, >100.0 μg/ml), Bacillus cereus (MICs 25.0, 50.0, 25.0 and 50.0 μg/ml) and Pseudomonas aeruginosa (MICs 50.0, >100.0, 50.0, >100.0 μg/ml) were assayed by micro-broth dilution. The results based on MIC data indicated that 2 and 4 exhibited significantly less potent antibacterial activities when compared to that of 1 and 3.

New Antifungal Pyranoisoflavone from Ficus tikoua Bur.

Considering the undesirable attributes of synthetic fungicides and the availability of Ficus species in China, the stem of Ficus tikoua Bur. was investigated. One new antifungal pyranoisoflavone, 5,3′,4′-trihydroxy-2″,2″-dimethylpyrano (5″,6″:7,8) isoflavone (1), together with two known isoflavones, wighteone (2) and lupiwighteone (3) (with previously reported antifungal activities), were isolated from ethyl acetate extract by bioassay-guided fractionation. Their structures were determined by spectroscopic analysis, such as NMR (1H-1H COSY, HMQC, HMBC and NOESY), IR, UV and HRMS, as well as ESI-MSn analyses. The antifungal activities of 1–3 against Phytophthora infestans were evaluated by direct spore germination assay, and the IC50 values were 262.442, 198.153 and 90.365 μg·mL−1, respectively.

Antibacterial Activity Composition of the Fermentation Broth of Streptomyces djakartensis NW35

The new compound Z-4-2 was isolated from the fermentation broth of Streptomyces djakartensis NW35, together with the known compound N-acetyltryptamine (Z-9-2) by bioassay-guided fractionation. Its chemical structure was elucidated as (E)-2-methoxy-1,4 naphthoquinone-1-oxime (Z-4-2) mainly by NMR analyses and MS spectral data. Their antibacterial activities against bacteria were evaluated by the filter paper method. The results of indicated that these compounds possess significant antibacterial activities.

Three novel cyclic hexapeptides from Streptomyces alboflavus 313 and their antibacterial activity.

Three novel cyclic hexapeptides, designated NW-G05 (1), NW-G06 (2) and NW-G07 (3), were isolated from the fermentation broth of Streptomyces alboflavus 313. Their structures were elucidated on the basis of extensive spectroscopic analysis, MS experiments, and chemical analysis. Their antibacterial activities against several strains of bacteria were evaluated by micro-broth dilution method. Among these compounds, NW-G06 (2) and NW-G07 (3) displayed highly antibacterial activity against gram-positive bacteria, but not gram negative ones. However, NW-G05 (1) was not active against all tested microorganisms.

Identification of streptothricin class antibiotics in the early-stage of antibiotics screening by electrospray ionization mass spectrometry.

Several streptothricin antibiotics have been studied by tandem mass spectrometry. The dominant product ions were derived from the C7-N bond cleavage which lead to lose streptolidine from the [M+H]+. The fragmentation pathways of key ions were described and certained by parent scan. According to the generalized principles, streptothricin isomers could be distinguished easily by the difference of CID spectra. A facile method based on ion-pair RP-HPLC coupled with electrospray ionization tandem mass spectrometry has been established for the analysis of streptothricins in the fermentation broth of Streptomyces qinlingensis. A total of 19 streptothricinlike compounds were identified or tentatively characterized based on their mass spectral data, and in which 11 were the first reported compounds. This could be used as an important de-replication method in the programs of screening novel antibiotics.

Isolation and Characterization of Two Novel Antibacterial Cyclic Hexapeptides from Streptomyces alboflavus 313

Two novel cyclic hexapeptides, designated NW‐G08 (1) and NW‐G09 (2), were isolated from the fermentation broth of Streptomyces alboflavus 313. Their structures were elucidated on the basis of extensive spectroscopic analysis, MS experiments, and chemical analysis. Their antibacterial activities against several strains of bacteria were evaluated by micro‐broth dilution method. NW‐G08 (1) and NW‐G09 (2) were highly antibacterial against Gram‐positive but not active against Gram‐negative bactaria. The minimum inhibitory concentrations (MICs) of 1 against Bacillus cereus, Bacillus subtilis, and Staphylococcus aureus were 6.25, 6.25, and 1.56 μg/ml, respectively. It is worth noting that 1 and 2 exhibited much higher activities against methicillin‐resistant Staphylococcus aureus (MRSA) than ampicillin, which implies that they might be potential candidates for the development of novel drugs against resistant pathogenic bacteria.

A New Benzofuran Glucoside from Ficus Tikoua Bur

From the water-soluble portion of the methanol extract of stems of Ficus tikoua Bur., a new benzofuran glucoside, named 6-carboxyethyl-5-hydroxybenzofuran 5-O-β-d-glucopyranoside (1), together with one known benzofuran glucoside (2) were isolated. Their structures were elucidated by 1D and 2D (1H-1H COSY, HMQC, and HMBC) NMR spectroscopy and HRMS techniques. The antioxidant activities of the isolated compounds were assayed based on the scavenging activities of DPPH free radical. Compounds 1 and 2 exhibited moderate antioxidant activities, and the IC50 values were 242.8 μg·mL−1 and 324.9 μg·mL−1, respectively.

Isolation, structure elucidation and antibacterial activities of streptothricin acids

Five streptothricin acids (compounds 1–5) were isolated by ion-exchange resin chromatography and preparative RP-HPLC from the fermentation broth of Streptomyces qinlingensis. Their structures were elucidated mainly by analyses of the IR, HR-EIS-MS and NMR spectral data. They were deduced as two known compounds, streptothricin F acid (1) and streptothricin D acid (2), and three new compounds, 12-carbamoylstreptothricin E acid (3), 12-carbamoylstreptothricin D acid (4) and N-acetyl-streptothricin D acid (5), respectively. The antibacterial activities of 1–5 against Escherichia coli, Bacillus subtilis, Staphylococcus aureus, Bacillus cereus and Pseudomonas aeruginosa were assayed by micro-broth dilution. Comparison of the MICs with streptothricin F and D showed that the antimicrobial activities of 1–5 were decreased significantly but varied with the structures.

Two piperazic acid-containing cyclic hexapeptides from Streptomyces alboflavus 313

Two novel cyclic hexapeptides, designated NW-G10 (1) and NW-G11 (2), were isolated from the fermentation broth of Streptomyces alboflavus 313. Their relative structures were elucidated on the basis of extensive spectroscopic analysis, and the absolute configurations of several constituent amino acids were determined by Marfey’s method. NW-G10 (1) and NW-G11 (2) exhibited significant activity against Gram-positive bacteria, such as Bacillus cereus, Bacillus subtilis and Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus (MRSA), but they are not active against gram negatives.